4 Pole Motor to a 2 Pole Pump

It needs to be noted that speed decreases with increase in no of poles (Ns=120f/P and Nr=Ns(1-s), where P is the no. of poles, f is the frequency, Ns is the synchronous speed, Nr is the rated speed & S is the slip for an induction motor).

The pumps are normally designed to run at a particular speed for acheiving the process plant objectives. So if u connect a 4 Pole motor (instead of a 2 pole motor) to this pump, it would run at reduced speed and hence the pre-defined process plant objectiive cannot be achieved resulting in reduced system efficiency of the whole plant.

Rgds

Thanks alot, but running this way wont damage the pump in any way right?

True, though it will do little for the pump's performance...

It will damage the pump only if there is no flow.

Flow (Q) will halve Q1 = (n1/n).Q

Power (P)will vary as P1 = (n1/n)3 (cubed).P

Head H total (pressure) will vary as H1 = (n1/n)2 (squared).Htotal

Google affinity laws.

Note that these are approximations.

Type of pump?

Usually as you reduce the speed the pump flow will be highly affected (as per affinity law it is proportional) and then the system pressure too will have effect (due to reduced flow)

Nothing will happen to pump due to reduced speed but the equipment that it is pumping to may be another story.

The worst case scenario if it is a centrifugal pump is that your pump will not develop enough pressure to overcome the head in the system, so you will not pump anything at all. In some cases the pump is being cooled by the flow of fluid through it, and wil no flow there is a risk of over heating the pump motor and bearings etc. Only your pump supplier can legitimately answer this question.

One possibility is that it will behave like a convector heater until some protective device opens the circuit feeding it.